Biodiversity chapters 15, 16 and 14

What is singularity?

All matter in the universe compressed into a point about the size of a dime

What was the Big Bang and when did it occur?

The expansion of all matter outward from singularity about 13.7 billion years ago

What particles came directly out of the Big Bang?

Photons and quarks, which later formed protons, neutrons, and light elements like hydrogen, helium and lithium

What are photons?

Particles of light with properties of both matter and energy

What are quarks?

Elementary particles that combine to form hadrons such as protons and neutrons

How did stars and planets form?

Clouds of hydrogen collapsed to form stars, and when stars died and exploded, they created heavier elements that formed planets and solar systems

What evidence supports the Big Bang theory?

1) Hubble expansion of galaxies 2) Abundance of hydrogen, helium and lithium 3) Cosmic microwave background radiation

When did Earth form?

About 4.6 billion years ago

What era lasted from 4.6 billion to 500 million years ago?

Precambrian Era

Where did scientists believe Earth’s early atmosphere came from?

Volcanic outgassing

What did the Miller Experiment (1950s) demonstrate?

Organic molecules like glucose, amino acids, and nitrogenous bases can form spontaneously and abiotically under early Earth conditions

Which molecule likely came first, DNA or RNA?

RNA

Why is RNA thought to have come before DNA

Because RNA can self-replicate, act as an enzyme, and be favored by selection

What is a protobiont?

A membrane containing biological molecules and RNA — a possible precursor to life

What are the three domains of life?

Bacteria, Archaea, and Eukarya

What are extremophiles?

Archaea that live in extreme environments with unique adaptations

What was the earliest trace of life?

Isoprenoid residues (~3.8 billion years old) found in rocks, made only by Archaeans

What are stromatolites?

Fossilized mats of cyanobacteria that are about 3.5 billion years old

Why are cyanobacteria important?

They were photosynthetic and produced oxygen, leading to Earth’s oxygen-rich atmosphere

What do banded iron formations indicate?

Oceans and the atmosphere became saturated with oxygen around 2.7 billion years ago

What were the three major outcomes of oxygen saturation?

1) End of abiotic molecule formation 2) Extinction of anaerobic organisms 3) Formation of the ozone layer

When did the earliest eukaryotic cells appear?

Around 1.9 billion years ago

What is “Snowball Earth”

A global glaciation event about 700 million years ago that may have caused mass extinction 

What was the Cambrian Explosion?

A sudden appearance of many recognizable organisms about 500 million years ago

What era began with the Cambrian Explosion?

The Paleozoic Era

What was the climate like during the Paleozoic Era?

Warm and humid

What major groups first appeared or diversified in the Paleozoic Era?

Plants (mosses, ferns), fish, amphibians, reptiles, and gymnosperms

What event ended the Paleozoic Era?

The Permian Mass Extinction (~250 million years ago)

What caused the Permian Mass Extinction?

Formation of Pangea and massive vulcanism, destroyed over 90% of higher taxa

What era followed the Paleozoic?

The Mesozoic Era (~250-65 million years ago)

What was the Mesozoic climate like?

Hot and dry

Which organisms dominated the Mesozoic Era?

Dinosaurs and reptiles — “Age of Reptiles”

What types of plants dominated during the Mesozoic Era?

Gymnosperms (cone-bearing plants)

What event ended the Mesozoic Era?

The K-T (Cretaceous-Tertiary) Mass Extinction (~65 million years ago)

What likely caused the K-T extinction?

A meteor strike that destroyed 65% of species, including most dinosaurs

What is the Cenozoic Era known as?

The “Age of Mammals,” with diversification of mammals, birds, and angiosperms

What is a capsid?

The protein shell of a virus

What are capsomeres?

The individual protein subunits of a viral capsid

What is inside the capsid?

The viral nucleic acid (DNA or RNA)

What are the main shapes of viral capsids?

Icosahedral, helical, and complex

What is a bacteriophage?

A virus that infects bacteria

What is a viral envelope?

A membrane covering the capsid found in animal viruses, derived from the host cell membrane

What do viral spike proteins do?

They allow viruses to infect new cells and are the only viral structures the immune system recognizes

Are viruses considered living?

No, because they can only reproduce by parasitizing a host cell

What does it mean that viruses are obligate parasites?

They require a host cell to reproduce

What is viral specificity?

Each virus targets one tissue in one species

What are the steps of the lytic cycle?

Infection → circularization → takeover → synthesis → lysis

What are the steps of the lysogenic cycle?

Infection → integration (prophage) → excision → circularization → takeover → synthesis → lysis

What is a prophage?

Viral DNA integrated into the host’s chromosome during the lysogenic cycle

What is a virulent virus?

A virus that continuously builds new viruses at a low rate without killing the host cell

What is a latent virus?

A virus that remains hidden and inactive, usually in neurons

What is an oncavirus?

A virus that can cause cancer by inserting into genes regulating cell division

What do vaccines do?

They prepare the immune system to recognize pathogens, reducing illness severity and duration

What is a live vaccine?

A vaccine that uses a closely related but less harmful live pathogen

What is an attenuated vaccine?

A vaccine using a lab-weakened version of the pathogen

What is an inactivated vaccine?

A vaccine that uses chemically altered pathogens that can’t infect cells

What is a subunit vaccine?

A vaccine that exposes the immune system to part of a pathogen (like a spike protein)

What is an mRNA vaccine?

A vaccine that gives cells mRNA instructions to make a recognition factor

What is a toxoid vaccine?

A vaccine that targets a toxic produced by the pathogen

What is speciation?

The appearance of a new species

What is the Morphological Species Concept?

Defines species based on anatomical similarities and differences

What is the Biological Species Concept?

Defines species as groups that can produce viable, fertile offspring

What is reproductive isolation?

A barrier that prevents two populations from interbreeding

What is genetic divergence?

Accumulation of different mutations in isolated populations over time

What are prezygotic barriers?

Barriers that prevent fertilization before a zygote is formed

What is mechanical isolation?

When reproductive parts no longer fit together

What is temporal isolation

When populations breed during different seasons or times

What is behavioral isolation?

When populations have different courtship rituals

What is ecological isolation?

When populations occupy different habitats or niches

What is gamete mortality?

When gametes die before fertilization, often in species with external fertilization

What are postzygotic barriers?

Barriers that occur after fertilization and affect hybrid offspring

What is reduced hybrid fertility?

When offspring are viable but sterile

What is hybrid breakdown?

When the second generation of hybrids is weak or nonviable

What is the Ecological Species Concept

Defines species by shared habitat and niche requirements

What is the Phylogenetic Species Concept?

Defines species by genetic similarity and differences in DNA sequences

What is allopatric speciation?

When geographic separation leads to new species (e.g., Grand Canyon)

What is sympatric speciation?

When new species arise without a geographic barrier

What is adaptive radiation?

A rapid diversification of species after a mass extinction as survivors fill vacant niches